script/cmds: add yq command for yaml manipulation.

go.mod

@@ -19,6 +19,7 @@ require (
 
 require (
 	github.com/fsnotify/fsnotify v1.7.0 // indirect
+	github.com/goccy/go-yaml v1.17.1 // indirect
 	github.com/google/go-cmp v0.6.0 // indirect
 	github.com/hashicorp/hcl v1.0.0 // indirect
 	github.com/inconshreveable/mousetrap v1.1.0 // indirect

go.sum

@@ -9,6 +9,8 @@ github.com/frankban/quicktest v1.14.6 h1:7Xjx+VpznH+oBnejlPUj8oUpdxnVs4f8XU8WnHk
 github.com/frankban/quicktest v1.14.6/go.mod h1:4ptaffx2x8+WTWXmUCuVU6aPUX1/Mz7zb5vbUoiM6w0=
 github.com/fsnotify/fsnotify v1.7.0 h1:8JEhPFa5W2WU7YfeZzPNqzMP6Lwt7L2715Ggo0nosvA=
 github.com/fsnotify/fsnotify v1.7.0/go.mod h1:40Bi/Hjc2AVfZrqy+aj+yEI+/bRxZnMJyTJwOpGvigM=
+github.com/goccy/go-yaml v1.17.1 h1:LI34wktB2xEE3ONG/2Ar54+/HJVBriAGJ55PHls4YuY=
+github.com/goccy/go-yaml v1.17.1/go.mod h1:XBurs7gK8ATbW4ZPGKgcbrY1Br56PdM69F7LkFRi1kA=
 github.com/google/go-cmp v0.6.0 h1:ofyhxvXcZhMsU5ulbFiLKl/XBFqE1GSq7atu8tAmTRI=
 github.com/google/go-cmp v0.6.0/go.mod h1:17dUlkBOakJ0+DkrSSNjCkIjxS6bF9zb3elmeNGIjoY=
 github.com/hashicorp/hcl v1.0.0 h1:0Anlzjpi4vEasTeNFn2mLJgTSwt0+6sfsiTG8qcWGx4=

script/cmds.go

@@ -5,6 +5,7 @@
 package script
 
 import (
+	"bytes"
 	"errors"
 	"fmt"
 	"io/fs"
@@ -19,6 +20,7 @@ import (
 	"time"
 
 	"github.com/cilium/hive/script/internal/diff"
+	yaml "github.com/goccy/go-yaml"
 	"github.com/spf13/pflag"
 	"golang.org/x/term"
 )
@@ -53,6 +55,7 @@ func DefaultCmds() map[string]Cmd {
 		"symlink": Symlink(),
 		"wait":    Wait(),
 		"break":   Break(),
+		"yq":      Yaml(),
 	}
 }
 
@@ -131,6 +134,49 @@ func Cat() Cmd {
 		})
 }
 
+func Yaml() Cmd {
+	return Command(
+		CmdUsage{
+			Summary: "concatenate files and print to the script's stdout buffer",
+			Args:    "files...",
+		},
+		func(s *State, args ...string) (WaitFunc, error) {
+			if len(args) == 0 {
+				return nil, ErrUsage
+			}
+
+			path := s.Path(args[0])
+			b, err := os.ReadFile(path)
+			var buf strings.Builder
+			buf.Write(b)
+			errc := make(chan error)
+			if err != nil {
+				errc <- err
+			} else {
+				close(errc)
+			}
+
+			wait := func(*State) (stdout, stderr string, err error) {
+				err = <-errc
+				if err != nil {
+					return "", "", err
+				}
+				path, err := yaml.PathString(args[1])
+				if err != nil {
+					return "", "", err
+				}
+				var out any
+				if err := path.Read(strings.NewReader(buf.String()), &out); err != nil {
+					return "", "", err
+				}
+				outBuf := &bytes.Buffer{}
+				yaml.NewEncoder(outBuf).Encode(out)
+				return outBuf.String(), "", err
+			}
+			return wait, nil
+		})
+}
+
 // Cd changes the current working directory.
 func Cd() Cmd {
 	return Command(

script/scripttest/testdata/yaml.txt

@@ -0,0 +1,17 @@
+yq pets.yaml '$.info.labels'
+cmp stdout labels.yaml
+-- labels.yaml --
+  labels:
+    foo: bar
+-- pets.yaml --
+info: 
+  name: "pets"
+  desc: "info about pets"
+  version: 7
+  labels:
+    foo: bar
+dogs:
+- "spot"
+- "jeff"
+cats:
+- "mittens"